Although the cost of a 40 Year Recertification can vary widely from professional to professional, there are certain basic items that can affect the cost. Either way, it is a good idea to understand what these potential issues are so you can discuss these with your engineer. Your engineer can provide you with a proposal once he has a good understanding of your building. Some engineers provide a price “per door” or per apartment. Prices can range between $10 per door to $300 per door (depending on many factors). Others provide a price based on square footage. Still others take into consideration the location or the structure, its age, and even if it has a crawl space that he may have to squeeze into.